Woolridge M W, Jackson D A, Imong S M, Yootabootr Y, Amatayakul K
Department of Child Health, University of Bristol, UK.
Hum Nutr Clin Nutr. 1987 Sep;41(5):347-61.
Indirect test weighing (ITW), for estimating night-time breast milk intake, is based on separate weighings of mother and infant before and after night-time sleep. Weight changes due to the exchange of milk overnight are reciprocal, so that if all other sources of weight change (eg, urine loss, supplementary fluid intake) are either controlled or measured, the difference between the mother's overnight weight loss and her infant's overnight weight gain represents their combined net evaporative water loss (EWL). The proportion of the combined EWL due to the infant is partitioned out as a function of the relative metabolic body sizes (kWt0.73) of mother and infant, and added to the infant's net overnight weight gain to provide an estimate of night-time breast milk intake. Validation studies, conducted in Northern Thailand, in which ITW was compared with direct test weighing (DTW) at each night feed, are reported for 13 infants over 3 nights at 5 d of age, and for 19 infants over 2 nights at 6 weeks of age or more. The regression equation for estimated milk intake against measured milk intake across all ages was y = 0.988x + 2.75, r = 0.927, n = 69 with 95 per cent prediction intervals of +/- 36 g for a range of intakes of 0-250 g. Rigorous control of data collection and taking account of the infant's age suggest that the prediction intervals for individual estimates can be improved to +/- 18 g at 5 d, and +/- 27 g at 6 weeks and over. Theoretical aspects of the relationship of EWL to body weight are discussed with a view to optimizing the accuracy of the technique.
间接测试称重法（ITW）用于估算夜间母乳摄入量，它基于对母婴在夜间睡眠前后分别进行称重。由于夜间母乳交换导致的体重变化是相互的，所以如果控制或测量了所有其他体重变化来源（如尿液流失、补充液摄入量），母亲夜间体重减轻与婴儿夜间体重增加之间的差值就代表了他们的综合净蒸发水分流失（EWL）。根据母婴相对代谢体重（kWt0.73）的函数关系，划分出婴儿在综合EWL中所占的比例，并将其加到婴儿夜间净体重增加量上，以估算夜间母乳摄入量。在泰国北部进行了验证研究，将ITW与每次夜间喂奶时的直接测试称重法（DTW）进行比较，报告了13名5日龄婴儿在3个晚上的情况，以及19名6周龄及以上婴儿在2个晚上的情况。所有年龄段估算母乳摄入量与测量母乳摄入量的回归方程为y = 0.988x + 2.75，r = 0.927，n = 69，对于0 - 250克的摄入量范围，95%的预测区间为±36克。严格控制数据收集并考虑婴儿年龄表明，对于个体估算，5日龄时预测区间可提高到±18克，6周龄及以上时可提高到±27克。讨论了EWL与体重关系的理论方面，以优化该技术的准确性。
